Geometry’s Answer: Spherical or Jet Explosions
After wrestling with the issue of GRB energies for years, astronomers realized the answer may have more to do with geometry than with radical new physics. The energy of a GRB may be radiated into space the way a supernova does, as a uniform spherical explosion spewing light and matter in all directions. If this is true, then the GRB radiation we pick up here on Earth is a tiny fraction of what has been radiated in all directions, and the energy of GRBs must be huge – many, many times larger than that of a supernova. On the other hand, what if GRBs are “jetted”, meaning all the energy comes out in a narrow focused beam? If this were the case, the radiation will not be detected in all directions, but only by those locations with the right orientation to the source. Jets occur in many astrophysical environments from the birth of young stars to the center of giant galaxies. What made jets so attractive to astronomers studying GRBs was the fact that limiting the GRB radiation to a jet, rather than spewing it across the whole sky, meant they did not have to produce so much energy. Instead of having to explain an explosion that was 1000 or 100 times larger than a supernova, astronomers now only had to deal with a factor of 10 - not so much of a stretch. Of course, making GRBs into jets means we are only seeing those bursts in which the jet is actually pointed in our direction. In the accompanying interactive you can explore how “jetting” changes the energy of a GRB.
|
